KUALA LUMPUR – Malaysia has arrested seven Philippine men suspected of involvement in activities of the Abu Sayyaf militant group, police said on Thursday, as concern grows in Southeast Asia over the possible expansion of militant Islamist activity.

The Abu Sayyaf, whose members have pledged loyalty to Islamic State, is notorious for bombings, beheadings, extortions and kidnap-for-ransom activities in the Philippines’ volatile south.

The men worked as security guards for private companies in the capital, Kuala Lumpur, and the surrounding state of Selangor, Inspector-General of Police Mohamad Fuzi Harun said.

“One suspect, a 22-year-old, was an Abu Sayyaf group member involved in clashes with the military and kidnapping of hostages in the southern Philippines,” he said in a statement.

An extremist faction of the Abu Sayyaf helped seize large parts of Marawi city in the southern Philippines in May, leading to a siege that has killed about 670 militants and 149 soldiers.

Reuters could not reach the men to seek comment as they are in custody. It was not immediately clear if they have lawyers to represent them.

Malaysian police said their arrests were based on information received after authorities thwarted a plan by an Abu Sayyaf member to stage an attack at the closing ceremony of the Southeast Asian Games in Kuala Lumpur last month.

All seven men arrived in Malaysia in September 2015 through the town of Sandakan in the state of Sabah on Borneo island, off the southern coast of the Philippines, before travelling to Kuala Lumpur on forged documents, Mohamad Fuzi said.

Since 2013, Muslim-majority Malaysia has detained more than 300 people with suspected links to Islamic State.